Process for testing spark stations



Patented Nov. 10, 1925.

UNITED STATES SIEGMUND LOEWE, 0F BERLIN, GERMANY.

PROCESS FOR TESTING SPARK STATIONS.

No Drawing.

Application filed July 2?, 1921. Serial No. 487,821.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. 1.,1313.)

To all whom it may concern:

Be it known that I, SIEGMUND Lonwn, a citizen of the German Republic,residing at Berlin, Germany, have invented certain new and usefulImprovements in Processes for Testing Spark Stations, (for which I havefiled applications in Germany, Sept. 15, 1915, now Patent 318,996;Denmark, Apr. 16, 1920; Poland, July 2, 1920; Sweden, Dec. 80, 1919), ofwhich the following is a specification.

Among the requirements for the proper working of a spark station is theemission of a pure tone. The production of this is accomplished eitherby adjustment to the proper potential or by processes which are knownunder the name of auxiliary sparking. The use of the auxiliary sparkbroadens the range of potential within which a good tone is obtained,without the potential regulation itself being entirely abandoned.

Testing as to whether the tone produced is pure or not, has previouslybeen accomplished by listening to the tone produced by means of acircuit containing a telephone and a detector, or by observing the sparkimage in a rotating helium tube.

Either method is only useful under very definite conditions, and is notsufficient for all requirements which might be set up. With thetelephone, for example, often the oscillation of the telephone membraneitself becomes so strong that the character of the tone is completelychanged. Likewise it is frequently found that the spark image to beobserved in the rotating helium tube has a relatively regularappearance, without the tone being pure.

Even more frequently the spark image observed is irregular for otherreasons; for example, if the number of revolutions of the driving motorfor the helium tube is not in a definite ratio to the sequence ofsparks, or, if the helium tube passes through fields of differentstrengths in its change of position, so that it lights more easily insome positions than in others.

Likewise at the detector, frequently, the reverse is the case:

In the detector circuit, the tone sounds poor, whereas in reality it isfound very good, upon testing by receiving at a distance.

In any event, heretofore, objective means have been lacking, whichindicate the quality of the tone.

By this invention, the process of testing the tone" is to be brought tothe form of a reading of an instrument or by the indication by such aninstrument. Several possibilities are offered for this. If it beobserved especially that a good tone can only occur if all phenomena inthe sending circuit repeat themselves very exactly in period; that apoor tone, on the contrary, is always present if any irregular phenomenacome into play; then it is immediately recognized that all means whichpermit deciding whether the phenomena in the sending circuit repeatthemselves with exact regularity or not, at the same time afiord thepossibility of investigating the quality of the tone. Let us take, forexample, the drop of potential at the condenser as a starting point fortesting the tone. A pure tone then is always produced if the drop ofpotential at the condenser exactly repeats itself periodically; theperiod of the repetition corresponding with the period of the generatortho it need not. It can, for example, be a higher or lower multiple ofthe same. It may also consist of groups which repeat themselvesperiodically (partial sparks).

.The problem now exists of determining whether the drop of potential atthe condenser repeats itself periodically or not; for example, whetherbesides its periodical repetition, more or less frequent disturbances ofthe drop of potential occur.

The indicating devices may have different properties. They may, forexample, respond to these disturbances; then the characteristic that agood tone is present would be that the instmmentremains in its positionof rest; or the instrument can as well respond to the periodicalphenomenon as well as to the disturbing one, then in most cases thecriterion for a good tone will consist in a. very quiet deviation of theinstrument. The instrument may finally only respond to theperiodicalphenomenon alone, then a measurement of the occurrence of disturbanceswould be found, for example, by the comparison of the energy expendedand that obtained in useful form (potential, current, output). Theinstrument itself in no way need be exclusively an electrical one; oftentimes the problem of investigating the phenomena in the sending circuitoi the station, with regard to their periodicity, may also be solved bymechanical or partly mechanical, partly electrical means, and mechanicalas well as electrical resonators are useful for.

this purpose.

The use of the process might be described by an example.

If we include, for example, an ordinary direct-current ammeter in theprimary circuit (exciting circuit) of a sending station for wirelesstelegraphy, then a slight reflection shows that this instrument can giveno deflection, it actually a spark is produced in the primary circuit ateach alternation, assuming that the spark which is produced by thepositive half-wave breaks at the same potential as that which gives thenegative halt-wave. The direct-current instrument is excitedballistically by each spark, and remains at rest, as the number ofcoulombs passing through the cross-section ol the conductor oil theprimary circuit is, under this assumption, equal but opposite in the twosparks; natural .y assuming that the number of sparks is suliicientlygreat so that the in strunient does not follow the individual sparkimpulses. It however only one spark occurs during each positivehaltwave.

to (l or assumes a constant value, wherewith in both cases, a pure toneis obtained under the circumstances.

in this case the characteristic for the occurrence ot a good tone islikewise that the indicator of the instrument remains at rest, indilierently where it be, whether at 0 or at any deflection. This deflectionshows, howover, much more at the same time. Under all conditions inwhich in equal times, the same inunber and the same strength, butoppositely directed sparks are produced, the instrui'nent remains atr'estand at O. This is, for example, the case if in each alterna tion orat the third, fifth, seventh a spark is produced (counting from thatalternation at which a spark was last produced). But if a spark passesat each sec- 0nd, fourth, sixth alternation, then the instrument shows aconstant positive or negative deflection.

The occurrence of a good tone can therefore not (only) be recognized bythe indicator remaining at rest, but also the form of the tone, whetherfundamental, third, octave, fifth, etc., by the reading of thedeficction of the indicator. In this modification, by way of example,there is therefore a directly-indieating instrument, in the, sense ofthe invention.

Further, the same instrument might also be intercalated at other pointsof the sending circuit; for example, in parallel to the exciting circuitcondenser or inthe secondary charging conductor of the transformer.Naturally, the damping of this instrument is to be so proportioned thaton the one hand it reacts sutliciently to the disturbances which occurin practice, on the other hand however not being immediately thrownacross the scale by every disturbance occurring.

Also, devices may be provided on the instrument which indicate theoccurrence of a good tone by the coming to restof a member whichoscillates at other times; or vice 'versa, by the starting to oscillateota membe' at other times remaining at rest. The inscription is selectedaccording to the construction of the instrun'ient; for example, so thatwhen an indicator comes to rest, an inscription is legible, for exampleTone good? Likewise the instrument may be directly calibrated in tones,so'that the occurrence of a fundamental, third, etc., can be read oil"directly.

.t would lead us too far to go into the numerous possibilities ofsolution which are still offered for the principle set up'here. To nameonly one further exampler Very definite, characteristic points and peaksexist in the shape of the curve of theprimary current at good tones,which naturally are to be referred to the disturbance of the course ofthe primary currentby the starting of the spark.

In the generator circuit of a sending station for wireless telegraphy,however, the instrument described above is not useful by itself, as inthis circuit a direct current can never occur. In spite of this, therecurrence of the same points and peaks in the curve for the current fora particular system, is typical of the occurrence of good tones.

It is well-known in alternating current 'technics how such distortionsof current may be observed (by resonators, etc.,).

Here the possibility is also offered of testing the presence of a goodtone by the occurrence of the peaks and points characteristic of a goodtone.

The most direct are naturally those methods which are based on thesparks themselves and their efiects; whether the indicator is ofoptical, thermal, mechanical, or electrical form, is of itself or noimportance; and it requires only some method of transmission to providea tone indicator in any manner, of the form described.

I claim:

1. The process of testing the purity of the tone of a radio sendingsystem, which consists in connecting a direct-current instrument to apart of the system undergoing periodical electrical changes andobserving whether the direct-current instrument gives a constantreading.

2. The process of testing the purity of tone of a radio sending systemwhich consists in connecting a direct-current ballistic instrument, sothat it is subjected to the changes in potential on a condenser of saidsystem and observing whether the reading of the instrument is constant.

3. The process of discriminating between the fundamental and overtoneswhile testing the purity of tone of a radio sending system, whichconsists in connecting a ballistic direct-current instrument so that itis subjected to the changes of potential on a condenser in said system,and observing whether the reading of the instrument is constant todetermine the purity of the tone and Whether the reading of theinstrument difions from zero to determine the presence oi harmonics inthe tone.

4. The process of adjusting a radio sending system to obtain purity oftone which consists in connecting a direct-current ballistic instrumentso that it is subjected to the potential upon a condenser of saidsystem,

observing the reading of the instrument, and adjusting the amplitude ofthe impressed potential until said reading is constant.

5. The process of determining whether the phenomena in a radio systemrepeat themselves exactly, which consists in applying to the system aninstrument that gives zero reading for exact repetition of said phenomena and a static reading other than zero for a repetition of a kindgiving rise to even harmonics.

6. The process of determining the purity of tone in a radio sendingsystem of the spark type, which consists in so connecting adirect-current instrument thereto that it is subjected to electricalchanges accom panying each spark, aid instrument being sufficientlydead-beat to prevent it responding to the changes accompanying a singlespark.

7. The process of discriminating, in testing the action of the radiosending system of the quenched spark type, between a single spark ineach half cycle and a plurality of sparks in each half cycle, whichconsists in so connecting a ballistic dead-beat directcurrent instrumentto the system that it is subjected to electrical changes accompanyingeach spark and observing Whether the reading of said instrument is zero.

8. The process of testing the purity of tone of a radio sending systemwhich consists in applying thereto an instrument responsive to the peakphenomena accompanying each period.

In testimony whereof I aflix my signature.

DR. SIEGMUND LOEWE.

